Measles Vaccine Failure in 9-month-old Infants

Objective: Lower seroconversion rates in live attenuated measles vaccines are detected in children aged 9 months or younger. We aimed to evaluate the effect of some infant characteristics (including growth status, yogurt consumption, infectious diseases, anemia, and serum zinc and selenium levels) on primary measles vaccine failure. Materials and Methods: We enrolled 147 healthy 9-month-old infants who were being attended to in the Social Pediatrics Unit for measles vaccination. Parameters, including maternal history of measles infection, vaccination status, infant sex, birth weight, gestational age, pattern of breastfeeding, amount of daily yogurt consumption, growth parameters, and history of infectious diseases, were recorded. Serum anti-measles IgG titers on Days 0 and 42, serum zinc and selenium levels on Day 0, and serum tumor necrosis factor (TNF)-alpha levels on Day 42 were analyzed. Results: Seroconversion rate was 62.6%. Among maternal and infant factors, the frequency of infant yogurt consumption of >= 75 mL/day was less in the non-seroconverted group (p=0.018). Multiple logistic regression analysis confirmed that the seroconversion rate was high in children with yogurt intake of >= 75 mL/day than in those with yogurt intake of <75 mL/day [OR: 2.85 (95% Cl: 1.12-7.24)]. Conclusion: More than one in three infants who were vaccinated at 9 months of age had primary vaccine failure. Nutritional status, including anemia and serum selenium and zinc levels, did not affect vaccine response. In future studies, the effect of yogurt consumption on seroconversion might be investigated.